(SELECT distinct O.orderdate, O.ordernum, 'x' as OpenEscalations
from tbl_order O
INNER JOIN tbl_escalation E on O.ordernum = E.ordernum
where E.escalation = 'open')
UNION ALL
(SELECT distinct O.orderdate, O.ordernum, ' '
from tbl_order O
LEFT JOIN tbl_escalation E on O.ordernum = E.ordernum and E.escalation = 'open'
where E.escalation IS NULL)
order by OpenEscalations desc, ordernum
Not the neatest solution, but as long as the data you are looking at is not huge it should be fast.
Jay